Science

genetic. The largest human family tree of all time

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Wherever we are, whoever we are, whatever our history and our ideology, there is a curiosity that unites people from all parts of the world: to know their origin. And as Jamaican activist Marcus Garvey said, “A people without knowledge of their history, origin and culture are like a tree without roots”. Recently, it was learned that humanity has “little genetic variation” and that this could jeopardize the future of human beings. According to Nature editor Henry Gee, when presenting his theory in Scientific American in early February, humanity will reach the “peak” by mid-century and begin to plummet. Before “everything ends”, and to “kill” curiosity about these “roots”, two groups of researchers from the University of Oxford, England, came together to determine the largest family tree of the story. And they succeeded, giving ‘unprecedented’ detail and showing the ‘wonderful’ way people around the world relate to each other: the unpublished study shows a network of almost 27 million people, some living and others extinct, retreating into interconnections over 100,000 years. The results were published in the journal Science.

According to Yan Wong, an evolutionary geneticist at the Big Data Institute and one of the study’s lead authors, in a press release, officials have constructed “a genealogy for all of humanity that models exactly how we can know history. which generated all the genetic variations that we find in humans today. “This genealogy allows us to see how the genetic sequence of each person is related to all the others, at all points of the genome”, explained the expert .

According to the study, “Individual genomic regions are inherited from a single parent (mother or father) and the ancestry of each point in the genome can be viewed as a tree.” The set of trees, known as the “tree sequence” or “ancestral recombination graph”, is what links “genetic regions in time to the ancestors where genetic variation first appeared”.

Wong and the rest of the team integrated data on modern and ancient human genomes from eight different databases, for a total of 3,609 individual genome sequences from 215 different populations. As for the ancient genomes, they included samples found across the globe with ages ranging from 1,000 to over 100,000 years.

In the prototype, algorithms can predict where common ancestors might be present in evolutionary trees to explain patterns of genetic variation. The resulting network contained nearly 27 million ancestors. Wong therefore believes that the study has just laid “the foundation for the next generation of DNA”: “As the quality of genomic sequences from modern and ancient DNA samples improves, trees will become many more and we can eventually generate a single, unified map that explains the descent of all the human genetic variations we see today.

An even more “complete” map After adding location data to the sample genomes, officials used the network to estimate where the predicted common ancestors lived, and the results ended up successfully “rescuing” key events in the history of the planet. human evolution, highlighting the migration out of Africa 70,000 years ago, which for the study means “the initial dispersal of Homo sapiens from East Africa into Eurasia”. Additionally, researchers have also uncovered potential evidence of interactions between Homo sapiens and now-extinct hominids such as the Denisovans.

Now the team plans to make the map “even more comprehensive” by continuing to incorporate genetic data as it becomes available. According to the officials, since tree sequences store data very efficiently, “the dataset can easily accommodate millions of additional genomes.”

According to Anthony Wilder Wohns, who carried out the research as part of his doctorate at the Big Data Institute and is now a postdoctoral fellow at the Broad Institute of MIT and Harvard, the new study “reconstructs the genomes of our ancestors and uses them to form a vast network of relationships”: “We can then estimate when and where these ancestors lived. The power of our approach is that it makes very few assumptions about the underlying data and can also include modern and ancient DNA samples. Nevertheless, Anthony Wilder Wohns believes the methodology could contribute to other areas of study, such as the evolution of all living things, such as orangutans and bacteria. “The methodology could benefit medical genetics, separating true associations between genetic regions and diseases from false connections stemming from our shared ancestral history,” he concluded.

A “decisive” contribution “Carried out within the framework of the Human Genome Project, not without the help of several scientists, including the North American Craig Venter, the deciphering and mapping of almost the entire human genome dates from the beginning of the present millennium”, begins with explain to the i Sónia Deus, professor of natural sciences and biology and geology. Twenty years later, the study published in the journal Science “announced the creation of the largest and most complete family tree of our species, a decisive contribution to the advancement of science in the field of genetics. “, defends the researcher.

“By crossing ancient DNA samples with modern genomic sequences, using increasingly sophisticated techniques and methods, it is now possible, on the one hand, to study human genetic evolution since the earliest times. more remote areas, and, on the other hand, to retrace the main migratory routes. flow of our ancestors”, underlines Sónia Deus, considering that among the conclusions to be drawn, “the low genetic variability of the samples used is surprising, which, in addition to other factors, could compromise the future of the human species” Furthermore, the official recalled that the discovery of DNA began in 1869, but its structure was not discovered until 1950. “There has been a rapid evolution in its study. This type of study can allow us not only to understand how the phylogenetic evolution of man has taken place over time, but also to discover the genetic basis of hereditary diseases, having application in their medical treatment and, with the advancement of studies, it will be possible to create more rigorous trees which make it possible to explain all the human variability existing on our planet”, reinforces the researcher.

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